The present invention relates to a medical device and consumables, and more particularly to a kit and directions used for separating and collecting cell-free plasma from finger stick blood samples to be used for genomic testing.
Typically, centrifugation is used to separate and collect cell-free plasma from blood samples; however, centrifugation is not always available at the point-of-collection and is not convenient for small blood volumes collected by finger stick. For small blood volumes, filtration membranes can be used to separate and collect plasma from blood samples. In a common method, a single filtration membrane is used for the separation and collection of plasma. In such method, blood samples may be applied to one end of the filtration membrane and as the blood sample flows through, blood cells may be separated from the plasma based on the size of the membranes pores. After filtration, the plasma containing portion of the membrane must be separated or severed from the blood cell-containing portion of the membrane, thereby necessitating an additional step of cutting the membrane prior to downstream plasma analysis. Furthermore, this single membrane approach may prevent using different materials and/or chemistries in the membranes for the separation and collection of plasma.
In another method, two separate membranes are used for the separation and collection of plasma by lateral flow. Specifically, a first membrane is used to filter and separate blood cells and a second membrane accepts or transfers the resulting cell-free plasma. These membranes may be arranged such that a distal end of the first membrane contacts a proximal end of the second membrane to facilitate the separation of blood cells via the first membrane and the collection of plasma via the second membrane by capillary flow.
Typically, devices for holding two membranes end-to-end with a minimal, but reproducible, overlap require a superior manufacturing tolerance that may not be compatible with low-cost manufacturing methods such as injection molding. Also, it may be difficult to apply uniform pressure at a contact area of the membranes to ensure consistent transfer of plasma from the separation membrane to the collection membrane without damaging the membranes.
With any blood collection and separation methods, there exists the potential to release genomic DNA from blood cells during the sample collection phase or separation phase. For membrane-based filtration and separation, this released genomic DNA is typically smaller than the pore size of the filtration membrane, and thus can flow with the plasma fraction. In downstream genomic analyses, this genomic DNA released ex vivo during sample collection and separation represents a contaminant species. This fact is especially pertinent to the genetic analysis of cell-free DNA, which is naturally released from cells into systemic circulation inside the body. Thus, the contamination of plasma with genomic DNA released ex vivo by non-optimal blood collection and separation can affect the desired analysis of natural cell-free DNA species released in vivo.
Thus, there is a need for an improved device or consumable that minimizes the release of genomic DNA from blood cells and facilitates proper holding and accurate positioning of two membranes used in plasma separation and collection. Moreover, there is a need for proper implementation of devices or consumable with finger stick blood samples such that DNA contamination is minimized during the process of preparing plasma from finger prick whole blood.